Field of the Invention
The present invention relates to a touch display panel, and in particular to a test method of the touch display panel capable of testing whether common electrode blocks are short-circuited or open-circuited and discharging pixel electrodes.
Description of the Related Art
The touch display panel means a display panel incorporated with touch function without a touch panel disposed on the touch panel. For example, a LCD panel or an OLED panel is incorporated with a touch function and called an in-cell touch display panel. Under this structure, the touch function is usually performed by utilizing the existing electrodes of the display panel. Thus, additional structures with touch function are not necessary. For example, if the in-cell touch display panel is a fringe field switching (FFS) type LCD panel, generally the common electrode is divided into a plurality of blocks operating as touch sensing electrodes.
A basic structure of the FFS type LCD panel is shown in FIG. 1. The FFS type LCD panel 10, from bottom to top, includes a lower polarizer 11, a lower substrate 12, a thin film transistor layer 13, a liquid crystal layer 14, an alignment layer 15, a color filter layer 16, an upper substrate 17, and an upper polarizer 18. The thin film transistor layer 13 further includes pixel electrodes 131, an insulating layer 132, a common electrode 133, and an alignment layer 134. When the pixel electrode 131 is supplied with voltage, an electric field is generated between the pixel electrode 131 and the common electrode 133. The generated electric field controls liquid crystal molecules spinning in the horizontal direction to adjust the gray level of the displaying image. In addition, a shielding layer can be disposed at a side of the color filter 16 facing the upper polarizer 18.
The common electrode of an usual FFS type LCD panel is an entire plane as the common electrode 133 shown in FIG. 1. In the touch display panel, the common electrode is divided into a plurality of electrode blocks. Each electrode block still operates as a common electrode during the display period, and operates as a touch sensing electrode during the touch sensing period to sense capacitance generated between the touch sensing electrode and an external touch object to determine the location of the touch object.
The plurality of electrode blocks divided from the common electrode have to be insulated to each other, so that the electrode blocks can separately detect the touch location. Therefore, each electrode block should be tested whether it is insulated to the others and operates normally before the touch display panel is assembled.